Preparation of hydrocarbon solvent solutions of organolithium compounds

ABSTRACT

Method of preparing hydrocarbon solvent solutions of organolithium compounds in which solutions such as benzene or heptane solutions of di- and poly-lithio adducts of polyisoprenes or polybutadienes containing strongly solvating ethers such as dimethyl ether or tetrahydrofuran are treated with weakly solvating ethers such as anisole, or weakly solvating tertiary amines such as triethylamine, to effect displacement from said solutions of the dimethyl ether or tetrahydrofuran. The resulting solutions are useful as catalysts in the production of conjugated polyene hydrocarbon polymers or copolymers thereof with vinylsubstituted aromatic hydrocarbons, having high cis-1,4 contents, as well as vinyl-substituted aromatic hydrocarbon polymers.

United States Patent Morrison et a1.

[54] PREPARATION OF HYDROCARBON SOLVENT SOLUTIONS OF ORGANOLITHIUMCOMPOUNDS Inventors: Robert C. Morrison, Conrad W.

Kama-18H, s h .a q.qiay,c- 28052 A Assignee: Lithium Corporation ofAmerica,

New York, N.Y.

Filed: Oct. 5, 1970 Appl. No.: 78,203

References Cited I UNITED STATES PATENTS 3,301,840 l/1967 Zelinski..260/94.2 M 3,377,404 4/1968 Zelinski ..260/665 R 3,388,178 6/1968Kamienski ..260/665 R Sept. 26, 1972 3,541,149 11/1970 Langer ..260/665R Primary Examiner-Tobias E. Levow Assistant Examiner-A. P. DemersAttorney-Wallenstein, Spangenberg, Hattis & Strampel [5 7] ABSTRACTMethod of preparing hydrocarbon solvent solutions of organolithiumcompounds in which solutions such as benzene or heptane solutions ofdiand poly-lithio adducts of polyisoprenes or polybutadienes containingstrongly solvating ethers such as dimethyl ether or tetrahydrofuran aretreated with weakly solvating ethers such as anisole, or weaklysolvating tertiary amines such as triethylamine, to effect displacementfrom said solutions of the dimethyl ether or tetrahydrofuran. Theresulting solutions are useful as catalysts in the production ofconjugated polyene hydrocarbon polymers or copolymers thereof withvinyl-substituted aromatic hydrocarbons, having high cis-l,4 contents,as well as vinyl-substituted aromatic hydrocarbon polymers,

25 Claims, No Drawings PREPARATION OF HYDROCARBON SOLVENT SOLUTIONS OFORGANOLITHIUM COMPOUNDS It is known to the art that the presence ofappreciable quantities of certain ethers, such as dimethyl ether,diethyl ether and tetrahydrofuran, in hydrocarbon solvent solutions oforganolithium compounds such as nbutyllithium or sec-butyllithiumchanges the manner in which these compounds affect the stereoregularpolymerization of conjugated dienes [c.f. A.V. Tobolsky and DE. Rogers JPolymer Science, 40, 73 (1959)]. Thus, for instance, in thepolymerization of isoprene using alkyllithium catalysts, it isimpossible to obtain any or any appreciable cis 1,4-microstructure inthe resultant polymer when appreciable quantities of such' ethers asdiethyl ether or tetrahydrofuran are present. It'was heretofore found,however, that, in the presence of weakly complexing ethers such asanisole or phenyl ether, high percentages of cis-1,4 microstructurecould be obtained, comparable to that obtained in hydrocarbon solventsalone. Thus, for example, 82 percent cis-l,4 polyisoprene microstructurewas obtained using phenyl ether as the solvent for polymerization. Ithas also heretofore been shown that a polyisoprene prepared using 1,4-dilithiol ,l ,4,4-tetraphenylbutane in a cyclohexane-anisole mediumpossessed a microstructure having the composition: 65-70 percent cis-1,4; -25 percent trans-1,4; and the remainder 3,4. .[c.f. LJ. Fettersand M. Morton, Macromolecules 2, 453 1969)]. A high cis-1,4microstructure is necessary to obtain. elastomeric properties in theresultant polydiene.

There is considerable literature extant describing the preparation ofsolutions of organodilithium compounds from lithium metal (c.f. forexample, US. Pats. No. 3,091,606; 3,278,617; 3,193,590; and 3,388,178).In all the cases cited, the ethers utilized are required in at leaststoichiometricquantities equivalent to the lithium metal in order toobtain reasonable yields of organodilithiums and to keep the resultantproduct in solution.

In U.S. Pat. No. 3,377,404, a modified procedure is shown in-whichether-free hydrocarbon-soluble diand poly-lithio'organicsaredescribed'Even here, however, a solution of the dilithioorganic isinitially prepared in a dialkyl ether such as diethyl ether or a cyclicether such as tetrahydrofuran. To this solution is then added sufficientconjugated diene to cause solubilization of the resulting chain-extendeddior poly-lithioorganic in a hydrocarbon medium when the ether isremoved. The ether solution is then distilled under vacuum to removemost of the solvent, and a hydrocarbon diluent added to the residue toeffect solubilization. Most of the residual ether is then removed by aseries of vacuum distillations and redilutions with a hydrocarbonsolvent. The difficulty in removing the residual ether is inherent inthe nature of the strong complexation thereof with organolithiumcompounds. For example, in US. Pat.

benzene solution, containing an equivalent of dimethyl ether, per C-Li,with isoprene eventually allows for the preparation of asoluble-dilithioorganic. Although the resultant product is almostcompletely soluble in benzene, it is also quite viscous and containssome undissolved product. These attributes are deleterious todimethylaniline and triethylamine, act as solvents or cosolvents forboth the lithium-isoprene or other lithiurn conjugated polyene adductsand their chain-extended counterparts. Further, these ethers act asexcellent displacing agents for the complexed portion of dimethyl etherin the lithiumisoprene adduct solutions in benzene described above andin U.S. Pat. No. 3,388,178. This allows the displaced dimethyl ether inthese solutions to be easily stripped out in a single distillation atlow temperatures, thus avoiding known thermal decomposition reactions.The resulting product is completely soluble even when it is diluted withmajor quantities of a hydrocarbon solvent such as benzene. Thechain-extended counterpart can then be produced directly by addition ofa conjugated 1,3- diene to this solution. Alternatively, the originallithium-isoprene adduct solution containing solvated dimethyl ether maybe chain-extended with more isoprene. Then, after addition of anisol orsimilarly acting cosolvents, the solution may be stripped under vacuumto remove the complexed or solvated dimethyl ether. The resulting orremaining product is a clear, fluid solution of the chain-extendeddilithio isoprene adduct in benzene-anisole. Such chain extensions aredesirably of slight character. Thus, while the amount of the additionalconjugated polyene hydrocarbon or vinyl-substituted hydrocarbon issomewhat variable to achieve the slight chain extension herecontemplated in the solutions made pursuant to the present invention, itwill usually be in the range of somewhat more than 1 up to about 3 molesper C-Li bond.

Mono-, diand poly-lithioorganics are amenable to this treatment.However, monolithioorganics such as nbutyland sec-butyllithium aregenerally soluble in hydrocarbon solvents in the absence of dialkylethers or tertiary amines and, hence, do not require the describeddisplacement technique.

On the other hand, diand poly-lithioorganics are not generally solublein hydrocarbon solvents in the absence of ethers or tertiary amines suchas dimethyl ether, diethyl ether, tetrahydrofuran, trimethylamine andmethyltriethylenediamine, and, therefore, the invention of the presentapplication is directed particularly to the treatment of solutions ofdiand polylithioorganics in mixtures of hydrocarbon solvents and suchethers which are of strongly solvating power. Dilithioorganics which canbe readily solubilized by the process of this invention are, forexample, those which result through the dimerization of variousconjugated dienes or vinylaromatic compounds with lithium metal,exemplified by l,3-dilithio-2,7-dimethylocta-2,6-diene; 2,4-dilithio,2,4-diphenyl-hexane; 1 ,4-dilithiol l ,4,4- tetraphenylbutane and1,8-dilithio-2,3,6,7-tetramethylocta-2,6-diene. Other types ofdilithioorganics, may also be solubilized as, for example, those derivedby lithiumhalogen exchange reactions. In this category are alkylenedilithiums such as, for example, l,4-dilithiobutane;1,5-dilithiopentane; 4,4-dilithiobiphenyl and 2,2-dilithiodiphenyloxide. Polylithioorganics, wherein there are 3 or 4lithiums in the molecule are shown, for instance, in U.S. Pat. No.3,377,404 the disclosure of which with respect thereto is herewithincorporated by reference. As shown in said US. Pat. No. 3,377,404, thepolylithioorganics can be identified by the formula RLi where x is aninteger from 2 to 4, and R is a hydrocarbon radical selected from thegroup consisting of aliphatic, cycloaliphatic and aromatic radicals.

The ethers which are useful in the practice of the present invention,and which serve to displace such ethers as dimethyl ether, diethyl etherand tetrahydrofuran, are liquids having weak-solvating properties andare generally alkyl aryl ethers, being exemplified by anisole, ethylphenyl ether, isopropyl phenyl ether, ethyl naphthyl ether, n-butylnaphthylether, dibenzyl ether, n-butyl phenyl ether, ethyl tolyl ether,isopropyl tolyl ether and, in general, C -C alkyl-aryl ethers; anddiaryl ethers such as diphenyl ether, dinaphthyl ether, di-p-tolyl etherand phenyl o-tolyl ether. The foregoing weakly solvating ethers aresharply distinguishable from the strongly solvating ethers such asdimethyl ether, diethyl ether, diamyl ether or other C -C or C C,dialkyl ethers, or cyclo ethers such as tetrahydrofuran andtetrahydropyran.

The tertiary amines which are useful in the practice of the presentinvention and which can be used to displace such ethers as dimethylether, diethyl ether and tetrahydorfuran, are liquids havingweak-solvating properties and are generally low molecular weighttrialkylamines which do not contain any methyl groups, illustrativeexamples of which are triethylamine, tri-npropylamine,tri-isopropylamine, ethyl di-n-butylamine and triisobutylamine and otherC -C alkyl tertiary amines. Aralkylamines can also be used, illustrativeexamples of which are dimethylaniline, diethylaniline,diisopropylaniline and methylisobutylaniline. Again, the foregoingweakly solvating aliphatic tertiary amines are sharply distinguishablefrom the strongly-solvating aliphatic tertiary amines such astrimethylamine, N,N,N',N'-tetramethylethylenediamine andmethyltriethylenediamine.

The term weakly solvating, as applied to the ethers and tertiary amines,is intended to mean those compounds of said chemical classes whoseeffect on the microstructure of polymers of conjugated dienes, notablyisoprene and 1,3-butyadiene, is substantially the same or littledifferent from that exerted by pure liquid hydrocarbon solvents such asbenzene, toluene, n-heptane, n-hexane and the like. Contrariwise,strongly solvating, as applied to ethers and tertiary amines, isintended to mean those compounds whose effect on the microstructure ofconjugated dienes, notably isoprene and 1,3-butadiene, is to producelittle (generally less than 10 percent) or no cis-l,4 microstructure inthe resulting polymer, which is very substantially different from whatis obtained in the presence of pure liquid hydrocarbons such as thosementioned above.

A variety of combinations is possible of the aforesaid weakly solvatingethers or tertiary amines and liquid hydrocarbon solvents in thepractice of the method of the present invention. The liquid hydrocarbonsolvents can be of aliphatic, cycloaliphatic, aromatic oraromatic-aliphatic character and are particularly exemplified byn-heptane, n-hexane, n-octane, isooctane, cyclopentane, cyclohexane,cyclooctane, benzene, toluene, ethyl benzene, propyl benzene, isopropylbenzene, and compatible mixtures of any two or more thereof. The weightratios of said weakly solvating ethers or tertiary amines to said liquidhydrocarbon solvents are variable within quite large ranges, and usuallywill fall within the range of from 5 to 95 percent of said weaklysolvating ethers or tertiary amines to 95 to 5 percent of said liquidhydrocarbon solvents. In general, however, it is desirable to keep theweakly solvating ethers or tertiary amines to a minimum since excessiveamounts thereof tend to exert a weak influence on the microstructure ofderivative polydienes, causing a decrease in the cis-l,4 content. A moredesirable range is from 5 to 50 percent of the weakly solvating ether oraliphatic tertiary amine to from 95 to 50 percent of the liquidhydrocarbon solvent, and especially advantageous is a range of 5 to 20percent of said ether or amine to 95 to 80 percent of said solvent, saidpercentages being by weight in relation to each other.

The following examples are further illustrative of the practice of theinvention, but they are not to be construed as in any way limitativethereof since various changes can readily be made and various othercompositions prepared in the light of the guiding principles andteachings disclosed herein. All temperatures recited are in degreesCentigrade.

In Examples 1 dimethyl and 2, comparisons are made among dimethylether-solvated dilithioorganics, unsolvated dilithioorganics, andorganics solvated with weakly solvated compounds in accordance wit thepresent invention.

EXAMPLE 1 a. Preparation of a diemt-yl ether-solvated dilithioorganic28.5g of lithium metal, as a 30 wt percent dispersion in mineral oil andhaving an average particle size of about 20 microns in diameter, wascharged to an argonswept reaction flask fitted with a mechanicalstirrer, thermometer, addition funnel and reflux condenser. The flaskwas cooled to -25". Then, 304 g of benzene was added to the dispersionand 5 g of dimethyl ether was condensed into the foregoing mixture. Theaddition funnel was filled with 255 g of isoprene. The temperature wasmaintained at -25 and stirring was begun. A benzene solution (0.8 Nconcentration) of a preformed dilithiopolyisoprene adduct was added.Then 5 g of isoprene was rapidly added to the reaction mixture in theflask. The reaction initiated immediately as indicated by a temperaturerise and the formation of a green color. The isoprene was slowly addedduring a 1-hour period. When the reaction was complete, the

excess dimethyl ether was removed and additional benzene was added toobtain a product 1.0 N in dilithiopolyisoprene adduct, The productsolution, containing a dilithiopolyisoprene adduct, was filtered toremove the unreacted lithium metal. The solution contained about 6 wtpercent dimethyl ether. b. Preparation of an unsolvated dilithioorganicfrom product (a) Approximately 1,000 ml of the product obtained in parta. of Example 1 was evaporated to dryness in a fvacuo. To the driedproduct 100 ml of n-heptane was added and the mixture stirred until thecake was broken up into small particles. The mixture was evaporatedto'dryness and the same process repeated twice, using benzene insteadofn-heptane. A vacuum of a fraction of a millimeter was applied forseveral hours at 4050. Then, n-pentane was added and the mixture stirredwhilethe solvent was slowly distilled. After 100 ml of distillatehadbeen collected, a sample of the residual slurry was hydrolyzed andassayed for dimethyl ether content by vapor phase chromatography. Thedimethyl ether content was found to be under 0.25 wt percent. Theproduct slurry was filtered and the solid dried to a powder by passagethrough it of a stream of dry argon. The product (24 g) was a fineorange powder which smokedand burned in air.

c. Preparation of an anisole solvated dilithioorganic from product (a) p400 mlof the product obtained in part a. of this example and 200 ml ofanisole were mixed in a 2-liter, 3-

necked flask. Afterstanding for about 12 hours, the flask and contentswere attached to a laboratory, rotating, flash-evaporator and about 300ml of solvents removed over a 3-hour period at a temperature of to 10anda vacuum of 12 mm. Analysis of the distillate showedthat very littleanisole hadbeenlost from the product solution. The residual solution wasclear and orange-red in color and was diluted with 100 ml of drybenzene. Analysis of the solution showed the total lithiumcontent to be1.29 N and the active carbon-lithium content to be 1.24 N. Gas-liquidchromatographic analysis showed that the dimethyl ether content had beenreduced to a level of 1 equivalent per 166 equivalents of carbon-lithiumbonds present.

It will thus be seen that the weakly solvating anisole has a boilingpoint (154 C) which is substantially higher than the boiling point ofthe strongly solvating dimethyl ether (-25 C), and thus, on saidevaporation, substantially all of the strongly solvating dimethyl etheris stripped out without substantial evaporation of the weakly solvatinganisole.

EXAMPLE 2 a. Preparation of a dimethyl ether-solvated adduct of lithiummetal'and 2,3-dimethylbutadiene 14 g of a 30 Wt percent lithiumdispersion in mineral oil (0.6 g atoms Li containing 1 wt percent of Na)was reacted with 0 g (0.6 moles) of 2,3-dimethyl-l,3-butadiene in 500 mlof dimethyl ether at -3 1. A volume of 250 ml of dry benzene was addedand the mixture allowed to warm to room temperature. An additional 300ml of benzene was then added. After filtration to remove unreactedlithium metal, a clear, fluid,-bright cherry red 1.16 N solution of thedilithio-adduct of said dimethyl-butadiene in benzene-dimethyl ether wasohtained. The yield of adduct based on lithium metal was percent.

b. Preparation of an Unsolvated Adduct of Lithium Metal and2,3-dimethylbutadiene Benzene and dimethyl ether solvents were removedfrom a ml portion of the 24 product by flash distillation. The dimethylether-free product was a yellow, crystalline material which was onlyslightly soluble in benzene (ca. 0.1 N).

0. Preparation of a N,N-dimethylanilinesolvated Adduct of Lithium Metaland 2,3-dimethyl Butadiene 350 ml of the product obtained in part a ofthis example and 150 ml of N,N-dimethylaniline were mixed together andtreated as described in Example 1. After removal of most of the benzeneand all of the dimethyl ether under vacuum, the residue was diluted with150 ml of dry benzene to yield a clear, red 1 N solution of the dilithioadduct of 2,3-dimethylbutadiene dimer in benzene-dimethylaniline. Thedimethyl ether content of this solution was determined to be less than 1equivalent per 100 equivalents of carbon-lithium.

' EXAMPLE 3 In this Example, a comparison is made between adilithioorganic in a trimethylamine-solvated system, in

a pure hydrocarbon'medium, and in .weakly solvated tertiary amine(N,N-dimethyl aniline) system.

a. Preparation of a Trimethylaminesolvated Dilithioorganic 5.33 g of alithium dispersion, 30 wt percent in mineral oil [1.6 g (0.23 g atoms)of lithium containing 0.5 wt percent sodium], and 5 ml of n-heptane wereplaced in a 300 ml, three-necked round-bottom flask equipped withmechanical stirrer, dry-ice condenser with gas inlet tube for argon, 100ml graduated dropping funnel, and gas-inlet tube for solvent. 1 ml of al N solution of the dilithio adduct of isoprene in benzene was added andthe mixture stirred for 15 minutes. 100 milliliters of trimethylamine(dried by passing through anhydrous CaSO was condensed into the flask. 2ml of isoprene, previously dried over powdered molecular sieves, wasadded to the stirred mixture at reflux (10). The color of the mixtureturned from silvery-grey to orange within a few minutes and the refluxrate increased. The remainder of the 25 ml (0.25 moles) of isoprene wasadded to the rapidly stirred mixture at reflux over a period of 45minutes. Toward the end of the addition, the mixture slowly turned froma deep orange-red to a light green color. Stirring was continued for 0.5hour after addition was complete. The solvent was allowed to boil offwith the aid of a warm water bath and the temperature gradually rose to24 over a period of 1 hour. 80 ml of benzene, previously dried overmolecular sieves, was added to the thick, stirred residue. Very littlemetal was left at this point, although some other solids were alsopresent. The clear, light yellow-orange solution, which was filteredaway from these solids, had a volume of ml and a total concentration of1.42 N. The yield of dilithio adducts of isoprene was 77 percent basedon initial lithium metal. Analysis of a sample of hydrolyzed solution byGLC showed that the dimer content (C H represented 90 percent of thetotal oligomers formed, the remainder being mainly trimer (C I-1H 7 b.Preparation of a N,N-dimethylaniline-solvated Dilithioorganic from aTrimethylamine-solvated Dilithioorganic 100 ml of the product solutionof the dilithio adduct of isoprene in benzene-trimethylamine prepared inExample 3(a) above was mixed with 50 ml of dry N,N dimethylaniline.After standing overnight, the product solution was stripped of benzeneand trimethylamine under vacuum on a rotating flash evaporator atambient temperature. Analysis of the distillate showed very little lossof dimethylaniline. The residual product solution was diluted with 50 mlof dry benzene. Analysis of the fluid, clear, orange-red solution showedthe total lithium content to be 1.3 N and the trimethylamine content tobe less than 1 equivalent per 100 equivalents of carbon-lithium bonds.

EXAMPLE 4 In this Example, a comparison is made between a chain-extendeddilithioorganic in dimethyl ether, in a pure hydrocarbon medium, and inanisole.

a. Preparation of a Dimethyl Ether-solvated, Chainextended Adduct ofLithium Metal and lsoprene A 5 liter, 3-necked flask was charged with 2liters of a l N solution of the adduct of lithium metal and isopreneprepared as described in Example 1(a). 272 g of freshly distilledisoprene was slowly added to the solution at a rate of about 1 ml perminute with stirring. The temperature of the reaction mixture was maintained at 30 throughout the 6.5 hour addition period. A clear, lightorange-red, fluid solution resulted.

b. Preparation of an Unsolvated, Chain-extended Adduct of Lithium Metaland lsoprene in Benzene The reaction flask and contents of the productsolution of part (a) of this Example were then attached to a heavy duty,rotating flash evaporator and the solvents removed under vacuum over an8-hour period. 1.5 liters of dry benzene was added to the residual solidmass of product and the mixture stirred overnight to obtain ahomogeneous, viscous, fine suspension of the product in benzene. Foursuch solvent strips and redilutions were required to lower the dimethylether content to 1 equivalent per 20 equivalents of carbon-lithium. A1.1 N light orange, viscous homogeneous suspension was obtained whichdid not settle in 4 days time. High speed centrifugation of the mixturefollowed by analysis of the clear supernatant solution showed thepresence in solution of approximately 75 percent of the total lithiumfound in the uncentrifuged suspension.

0. Preparation of an Anisole-solvated, Chain-extended Adduct of LithiumMetal and lsoprene in Benzene 250 ml of a l N solution of the adduct oflithium metal and isoprene, prepared as described in Example 1(a), wastreated with 0.5 mole of isoprene as described in Example 4(a). Then,1.15 moles of anisole was added to the resulting product solution. Afterstanding overnight, the solution was attached to a rotating flashevaporator and most of the benzene and essentially all of the dimethylether removed under vacuum in 2.5 hours at 0 to 10. 225 ml of benzenewas added to the slightly viscous product solution. GLC analysis of theclear, fluid solution showed that the dimethyl ether content had beenreduced from an original 1 equivalent per 1.2 carbon-lithiums to 1equivalent per 72 carbon-lithiums.

d. Preparation of an Anisole-solvated, Chain-extended Adduct of LithiumMetal and lsoprene 3 liters of a solution of the adduct of lithium andisoprene, prepared as described in Example 1(a), was chain-extended with600 ml of isoprene as described in Example 4(a). 600 ml of anisole wasstirred into the product. The product solution as divided into 2 equalparts and each part stripped on the rotating flash evaporator forapproximately 4.5 hours. Both residues were recombined and 1.15 litersof dry benzene added, with stirring. The resulting clear, fluid, darkamber solution was found to be 1.18 N in total lithium and 1.11 N inactive carbon lithium content. It contained approximately volume percentanisole.

The weakly solvated ether or tertiary amine hydrocarbon solventsolutions of the dior polylithioorganics, as indicated above, are highlyuseful for the production of conjugated polyene, particularly conjugateddiene, polymers, and copolymers with vinylsubstituted aromatichydrocarbons, having high cisl ,4 contents, of the order of 40 percentto percent or more in various cases, depending upon the monomerutilized, and for the production of polymers derived fromvinyl-substituted aromatic hydrocarbon monomers. Such monomers are wellknown to the art, as are the polymers and copolymers thereof, and areshown, for instance, in U. S. Pat. Nos. 3,091,606 and 3,377,404, thedisclosures with respect thereto being incorporated herein by reference.

What is claimed is:

1. In a method of preparing a solvated lithium metal adduct of at leastone member selected from the group consisting of (a) conjugated polyenehydrocarbon monomers, (b) vinyl-substituted aromatic hydrocarbonmonomers, (c) mixtures of (a) and (b), and (d) their slightlychain-extended oligomers, which comprises providing a solution, in anorganic solvent which includes at least one member selected from thegroup consisting of volatile liquid inert strongly solvating dialkylethers, cyclic ethers and tertiary amines, of at least one diorpoly-lithio adduct selected from the aforesaid (a), (b), (c) and (d)groups, admixing said solution with at least one member selected fromthe group consisting of weakly-solvating liquid ethers and weaklysolvating liquid tertiary amines, said weakly solvating compounds havinga boiling point substantially higher than the boiling point of saidstrongly solvating compound, and evaporating from said mixturesubstantially all of said strongly solvating compound withoutsubstantial evaporation of said weakly solvating compound.

2. In a method of preparing a solvated lithium metal adduct of at leastone member selected from the group consisting of (a) conjugated polyenehydrocarbon monomers, (b) vinyl-substituted aromatic hydrocarbonmonomers, (c) mixtures of (a) and (b), and (d) their slightlychain-extended oligomers, which comprises providing a solution, in amixture of a volatile liquid hydrocarbon solvent with at least onemember selected from the group of volatile liquid inert stronglysolvating dialkyl ethers, cyclic ethers and tertiary amines, of at leastone dior poly-lithio adduct selected from the aforesaid (a), (b), (c)and (d) groups, admixing said solution with at least one member selectedfrom the group consisting of weakly-solvating liquid ethers and weaklysolvating liquid tertiary amines, said weakly solvating compounds havinga boiling point substantially higher than the boiling point of saidstrongly solvating compound, and evaporating from said mixturesubstantially all of said strongly solvating compound withoutsubstantial evaporation of said weakly solvating compound.

3. The method of claim 2, wherein the liquid hydrocarbon solvent has aboiling point such that the evaporation is also effective to remove asubstantial part of the liquid hydrocarbon solvent, and then adding aliquid hydrocarbon solvent to produce a solution of said adduct in amixture containing said weakly solvating compound and liquid hydrocarbonsolvent in a weight ratio of 50 to 50 of said weakly solvating compoundto 95 to 50 of said liquid hydrocarbon solvent.

4. The method of claim 1, wherein the evaporation is effected by flashevaporation.

5. The method of claim 2, wherein the evaporation is effected by flashevaporation.

6. The method of claim 1, wherein the conjugated polyene hydrocarbon isat least one member selected from the group consisting of isoprene andl,3-butadiene, and the adduct is a dilithio adduct.

7. The method of claim 2, wherein the conjugated polyene hydrocarbon isat least one member selected from the group consisting of isoprene andl,3-butadiene, and the adduct is a dilithio adduct.

8. The method of claim 1, wherein the strongly solvating compound is atleast one member selected from the group consisting of C C dialkylethers and cyclic ethers. 9. The method of claim 2, wherein the stronglysolvating compound is at least one member selected from the groupconsisting of C C dialkyl ethers and cyclic ethers.

10. The method of claim 2, wherein the weakly solvating'compound is atleast one member selected from the group consisting of alkyl aryl ethersand diaryl ethers.

11. The method of claim 8, wherein the weakly solvating compound is atleast one member selected from the group consisting of alkyl aryl ethersand diaryl ethers.

12. The method of claim 10, wherein the weakly solvating ether'comprisesanisole.

13. The method of claim 11, wherein the weakly solvating ether comprisesanisole.

14. The method of claim 10, wherein the liquid hydrocarbon comprisesbenzene.

15. The method of claim 12, wherein the liquid hydrocarbon comprisesbenzene.

16. In a method of preparing a solvated lithium metal adduct of a memberselected from the group consisting of conjugated polyene hydrocarbonsand vinyl-substituted aromatic hydrocarbons wherein lithium metal isreacted with said conjugated polyene hydrocarbon monomer orvinyl-substituted aromatic hydrocarbon monomer in the presence of memberselected from the group consisting of volatile inert liquid dialkylethers and cyclic ethers and a liquid hydrocarbon solvent, to producesaid lithium metal adduct, and removing the unreacted lithium metal fromthe solution of said adduct, the improvement which comprises admixingsaid solution with a member selected from the group consistin of weak]solvati li uid eth rs nd weak] s lvating liquid ter tiary am ies havingoifing points su bstantially higher than the boiling point of saidweakly solvating compounds, and evaporating from said mixturesubstantially all of said dialkyl ether or cyclic ether withoutsubstantial evaporation of said weakly solvating compound.

17. The method of claim 16, wherein the liquid hydrocarbon solvent has aboiling point such that the evaporation is also effective to remove asubstantial part of the liquid hydrocarbon solvent to produce a solutionof said adduct in a mixture containing said weakly solvating compoundand liquid hydrocarbon solvent in a weight ratio of 5 to 50 of saidweakly solvating compound to to 50 of said liquid hydrocarbon solvent.

18. The method of claim 16, wherein the evaporation is effected by flashevaporation.

19. The method of claim 16, wherein the conjugated polyene hydrocarbonis at least one number selected from the group consisting of isopreneand l,3-butadiene.

20. The method of claim 16, wherein the weakly solvating ether is atleast one member selected from the group consisting of alkyl aryl ethersand diaryl ethers.

21. The method of claim 20, wherein the dialkyl and cyclic ethers areselected from the group consisting of dimethyl ether, diethyl ether andtetrahydrofuran, and wherein the weakly solvating ether comprisesanisole.

22. The method of claim 21, wherein the liquid hydrocarbon is a memberselected from the group consisting of benzene, toluene, n-heptane andn-hexane.

23. The method of claim 17, which includes the step of chain-extendingthe monomer by the addition thereto of a conjugated polyene hydrocarbon.

24. The method of claim 23, wherein said chain-extension is effectedafter the evaporation of said dialkyl ether or cyclic ether.

25. The method of claim 24, wherein said chain-extension is effectedprior to the evaporation of said dialkyl ether or cyclic ether.

2. In a method of preparing a solvated lithium metal adduct of at leastone member selected from the group consisting of (a) conjugated polyenehydrocarbon monomers, (b) vinyl-substituted aromatic hydrocarbonmonomers, (c) mixtures of (a) and (b), and (d) their slightlychain-extended oligomers, which comprises providing a solution, in amixture of a volatile liquid hydrocarbon solvent with at least onemember selected from the group of volatile liquid inert stronglysolvating dialkyl ethers, cyclic ethers and tertiary amines, of at leastone di- or poly-lithio adduct selected from the aforesaid (a), (b), (c)and (d) groups, admixing said solution with at least one member selectedfrom the group consisting of weakly-solvating liquid ethers and weaklysolvating liquid tertiary amines, said weakly solvating compounds havinga boiling point substantially higher than the boiling point of saidstrongly solvating compound, and evaporating from said mixturesubstantially all of said strongly solvating compound withoutsubstantial evaporation of said weakly solvating compound.
 3. The methodof claim 2, wherein the liquid hydrocarbon solvent has a boiling pointsuch that the evaporation is also effective to remove a substantial partof the liquid hydrocarbon solvent, and then adding a liquid hydrocarbonsolvent to produce a solution of said adduct in a mixture containingsaid weakly solvating compound and liquid hydrocarbon solvent in aweight ratio of 50 to 50 of said weakly solvating compound to 95 to 50of said liquid hydrocarbon solvent.
 4. The method of claim 1, whereinthe evaporation is effected by flash evaporation.
 5. The method of claim2, wherein the evaporation is effected by flash evaporation.
 6. Themethod of claim 1, wherein the conjugated polyene hydrocarbon is atleast one member selected from the group consisting of isoprene and1,3-butadiene, and the adduct is a dilithio adduct.
 7. The method ofclaim 2, wherein the conjugated polyene hydrocarbon is at least onemember selected from the group consisting of isoprene and 1,3-butadiene,and the adduct is a dilithio adduct.
 8. The method of claim 1, whereinthe strongly solvating compound is at least one member selected from thegroup consisting of C2-C8 dialkyl ethers and cyclic ethers.
 9. Themethod of claim 2, wherein the strongly solvating compound is at leastone member selected from the group consisting of C2-C8 dialkyl ethersand cyclic ethers.
 10. The method of claim 2, wherein the weaklysolvating compound is at least one member selected from the groupconsisting of alkyl aryl ethers and diaryl ethers.
 11. The method ofclaim 8, wherein the weakly solvating compound is at least one memberselected from the group consisting of alkyl aryl ethers and diarylethers.
 12. The method of claim 10, wherein the weakly solvating ethercomprises anisole.
 13. The method of claim 11, wherein the weaklysolvating ether comprises anisole.
 14. The method of claim 10, whereinthe liquid hydrocarbon comprises benzene.
 15. The method of claim 12,wherein the liquid hydrocarbon comprises benzene.
 16. In a method ofpreparing a solvated lithium metal adduct of a member selected from thegroup consisting of conjugated polyene hydrocarbons andvinyl-substituted aromatic hydrocarbons wherein lithium metal is reactedwith said conjugated polyene hydrocarbon monomer or vinyl-substitutedaromatic hydrocarbon monomer in the presence of member selected from thegroup consisting of volatile inert liquid dialkyl ethers and cyclicethers and a liquid hydrocarbon solvent, to produce said lithium metaladduct, and removing the unreacted lithium metal from the solution ofsaid adduct, the improvement which comprises admixing said solution witha member selected from the group consisting of weakly solvating liquidethers and weakly solvating liquid tertiary amines having boiling pointssubstantially higher than the boiling point of said weakly solvatingcompounds, and evaporating from said mixture substantially all of saiddialkyl ether or cyclic ether without substantial evaporation of saidweakly solvating compound.
 17. The method of claim 16, wherein theliquid hydrocarbon solvent has a boiling point such that the evaporationis also effective to remove a substantial part of the liquid hydrocarbonsolvent to produce a solution of said adduct in a mixture containingsaid weakly solvating compound and liquid hydrocarbon solvent in aweight ratio of 5 to 50 of said weakly solvating compound to 95 to 50 ofsaid liquid hydrocarbon solvent.
 18. The method of claim 16, wherein theevaporation is effected by flash evaporation.
 19. The method of claim16, wherein the conjugated polyene hydrocarbon is at least one numberselected from the group consisting of isoprene and 1,3-butadiene. 20.The method of claim 16, wherein the weakly solvating ether is at leastone member selected from the group consisting of alkyl aryl ethers anddiaryl ethers.
 21. The method of claim 20, wherein the dialkyl andcyclic ethers are selected from the group consisting of dimethyl ether,diethyl ether and tetrahydrofuran, and wherein the weakly solvatingether comprises anisole.
 22. The method of claim 21, wherein the liquidhydrocarbon is a member selected from the group consisting of benzene,toluene, n-heptane and n-hexane.
 23. The method of claim 17, whichincludes the step of chain-extending the monomer by the addition theretoof a conjugated polyene hydrocarbon.
 24. The method of claim 23, whereinsaid chain-extension is effected after the evaporation of said dialkylether or cyclic ether.
 25. The method of claim 24, wherein saidchain-extension is effected prior to the evaporation of said dialkylether or cyclic ether.